1. Field of the Invention
The present invention relates to a spatial switch using an optical beam steering device, and more particularly, to a spatial switch using a "M.times.N" optical beam steering device which operates with M "1.times.N" spatial switches using a phased optical waveguide array.
2. Description of the Related Art
According to the conventional technique of manufacturing a spatial switch device in the technical field of integrated optics, the spatial switch device is formed of switching nodes, and passive channel waveguides connecting the switching nodes to input and output ends. The method of connecting the switching nodes to input and output ends varies according to system requirements, and thus various kinds of switching network were implemented in the field of integrated optics. Typical examples of these switching networks will be described hereinbelow.
There has been proposed a 4.times.4 cross-bar network spatial switch which uses a 2.times.2 switch of the .DELTA..beta. reversal directional coupler type at LiNbO.sub.3 as a basic switching node (2,2,2 node). In this type of spatial switch, it is difficult to allow a 2.times.2 switch to have uniform characteristics at all nodes. The number of nodes abruptly increases as the number of input/output channels increase, which results in the increase of a cross-talk and losses. As another type of spatial switch, a32.times.32 spatial switch has been implemented based on a polarization independent 8.times.8 spatial switch of a simplified tree structure.
One of the severe problems encountered with these conventional spatial switches lies in that it is difficult to design the switch device due to the difficulty in manufacturing a switching node, the physical connection among the input, output and switching nodes by a channel waveguide, etc. Further, it is difficult to allow all nodes within a spatial switch to have uniform characteristics. And the number of nodes abruptly increases as the number of input/output channels increase. Also, the number of physical intersections between channel waveguides increases, which results in the increase of a cross-talk between channels and incurs the necessity of increasing the length of spatial the switch device. In accordance therewith, a propagation loss also increases. Lastly, other disadvantages include the complexity of the structure, difficulty of manufacturing, high costs, and low throughput.